When a liquid is cooled, the average energy of the molecules decreases.

At some point, the amount of heat removed is great enough that the attractive
forces between molecules draw the molecules close together, and the liquid
freezes to a solid.

Microscopic view
of a liquid.

Microscopic view
of a solid.

The temperature of a freezing liquid remains constant, even when more heat
is removed.

The freezing point of a liquid or the melting point
of a solid is the temperature at which the solid and liquid phases
are in equilibrium.

The rate of freezing of the liquid is equal to the
rate of melting of the solid and the quantities of solid and liquid remain
constant.

Factors That Affect Freezing Point

Types of Molecules: the types of molecules that make up a
liquid determine its freezing point. If the intermolecular forces between
molecules are:

relatively strong, the freezing point will be relatively
high.

relatively weak, the freezing point will be relatively
low.

= C

= O

= H

methyl ether (C2H6O)The freezing point of methyl ether is -138.5oC. The relatively weak dipole-dipole forces and London dispersion forces between molecules results in a lower freezing point compared to ethyl alcohol.

ethyl alcohol (C2H6O)The freezing point of ethyl alcohol is -117.3oC. Although dipole-dipole forces and London dispersion forces also exist between ethyl alcohol molecules, the strong hydrogen bonding interactions are responsible for the higher freezing point compared to methyl ether.